I have been reading about fungal sinus infections, what you described sounds like a "fungal ball" I have read about...if it is...lucky you because my readings say it has to be removed by surgery.
Sounds like a sinus infection. I get them all the time, and I do the same thing in the shower. It's gross, but it gets all the gunk out. I don't think whatever came out was anything to be too worried about. Have you had any surgery done to your sinuses. I had surgery a few months ago and sometimes when I do that, some scar tissue comes out, and brings some blood. My ENT says that it is completely normal, as long as it does not create any pain in the sinus or nose (headaches don't count) and there is no excessive bleeding. Just go see you doctor, antibiotics are probably best. Just a tip, if you do go, don't accept a Z-pack. They are fast, but a lot of people are resistant to them, and f you just don't try it, you might save yourself a wasted perscription and another visit to the doctor.
Good Luck!